EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)

CERN-PH-EP-2014-081LHCb-PAPER-2014-010

May 7, 2014 / revised June 18, 2014

Measurement of the Ξ−b and Ω−

bbaryon lifetimes

The LHCb collaboration†

AbstractUsing a data sample of pp collisions corresponding to an integrated luminosityof 3 fb−1, the Ξ−b and Ω−b baryons are reconstructed in the Ξ−b → J/ψΞ− andΩ−b → J/ψΩ− decay modes and their lifetimes measured to be

τ(Ξ−b ) = 1.55 +0.10−0.09 (stat)± 0.03 (syst) ps,

τ(Ω−b ) = 1.54 +0.26−0.21 (stat)± 0.05 (syst) ps.

These are the most precise determinations to date. Both measurements are in goodagreement with previous experimental results and with theoretical predictions.

Published in Phys. Lett. B 736, 154-162 (2014)

c© CERN on behalf of the LHCb collaboration, license CC-BY-3.0.

†Authors are listed on the following pages.

arX

iv:1

405.

1543

v2 [

hep-

ex]

15

Aug

201

4

ii

LHCb collaboration

R. Aaij41, B. Adeva37, M. Adinolfi46, A. Affolder52, Z. Ajaltouni5, J. Albrecht9, F. Alessio38,M. Alexander51, S. Ali41, G. Alkhazov30, P. Alvarez Cartelle37, A.A. Alves Jr25,38, S. Amato2,S. Amerio22, Y. Amhis7, L. An3, L. Anderlini17,g, J. Anderson40, R. Andreassen57,M. Andreotti16,f , J.E. Andrews58, R.B. Appleby54, O. Aquines Gutierrez10, F. Archilli38,A. Artamonov35, M. Artuso59, E. Aslanides6, G. Auriemma25,n, M. Baalouch5, S. Bachmann11,J.J. Back48, A. Badalov36, V. Balagura31, W. Baldini16, R.J. Barlow54, C. Barschel38,S. Barsuk7, W. Barter47, V. Batozskaya28, Th. Bauer41, A. Bay39, J. Beddow51, F. Bedeschi23,I. Bediaga1, S. Belogurov31, K. Belous35, I. Belyaev31, E. Ben-Haim8, G. Bencivenni18,S. Benson38, J. Benton46, A. Berezhnoy32, R. Bernet40, M.-O. Bettler47, M. van Beuzekom41,A. Bien11, S. Bifani45, T. Bird54, A. Bizzeti17,i, P.M. Bjørnstad54, T. Blake48, F. Blanc39,J. Blouw10, S. Blusk59, V. Bocci25, A. Bondar34, N. Bondar30,38, W. Bonivento15,38, S. Borghi54,A. Borgia59, M. Borsato7, T.J.V. Bowcock52, E. Bowen40, C. Bozzi16, T. Brambach9,J. van den Brand42, J. Bressieux39, D. Brett54, M. Britsch10, T. Britton59, N.H. Brook46,H. Brown52, A. Bursche40, G. Busetto22,q, J. Buytaert38, S. Cadeddu15, R. Calabrese16,f ,M. Calvi20,k, M. Calvo Gomez36,o, A. Camboni36, P. Campana18,38, D. Campora Perez38,A. Carbone14,d, G. Carboni24,l, R. Cardinale19,38,j , A. Cardini15, H. Carranza-Mejia50,L. Carson50, K. Carvalho Akiba2, G. Casse52, L. Cassina20, L. Castillo Garcia38, M. Cattaneo38,Ch. Cauet9, R. Cenci58, M. Charles8, Ph. Charpentier38, S.-F. Cheung55, N. Chiapolini40,M. Chrzaszcz40,26, K. Ciba38, X. Cid Vidal38, G. Ciezarek53, P.E.L. Clarke50, M. Clemencic38,H.V. Cliff47, J. Closier38, V. Coco38, J. Cogan6, E. Cogneras5, P. Collins38,A. Comerma-Montells11, A. Contu15,38, A. Cook46, M. Coombes46, S. Coquereau8, G. Corti38,M. Corvo16,f , I. Counts56, B. Couturier38, G.A. Cowan50, D.C. Craik48, M. Cruz Torres60,S. Cunliffe53, R. Currie50, C. D’Ambrosio38, J. Dalseno46, P. David8, P.N.Y. David41,A. Davis57, K. De Bruyn41, S. De Capua54, M. De Cian11, J.M. De Miranda1, L. De Paula2,W. De Silva57, P. De Simone18, D. Decamp4, M. Deckenhoff9, L. Del Buono8, N. Deleage4,D. Derkach55, O. Deschamps5, F. Dettori42, A. Di Canto38, H. Dijkstra38, S. Donleavy52,F. Dordei11, M. Dorigo39, A. Dosil Suarez37, D. Dossett48, A. Dovbnya43, F. Dupertuis39,P. Durante38, R. Dzhelyadin35, A. Dziurda26, A. Dzyuba30, S. Easo49,38, U. Egede53,V. Egorychev31, S. Eidelman34, S. Eisenhardt50, U. Eitschberger9, R. Ekelhof9, L. Eklund51,38,I. El Rifai5, Ch. Elsasser40, S. Esen11, T. Evans55, A. Falabella16,f , C. Farber11, C. Farinelli41,N. Farley45, S. Farry52, D. Ferguson50, V. Fernandez Albor37, F. Ferreira Rodrigues1,M. Ferro-Luzzi38, S. Filippov33, M. Fiore16,f , M. Fiorini16,f , M. Firlej27, C. Fitzpatrick38,T. Fiutowski27, M. Fontana10, F. Fontanelli19,j , R. Forty38, O. Francisco2, M. Frank38, C. Frei38,M. Frosini17,38,g, J. Fu21,38, E. Furfaro24,l, A. Gallas Torreira37, D. Galli14,d, S. Gallorini22,S. Gambetta19,j , M. Gandelman2, P. Gandini59, Y. Gao3, J. Garofoli59, J. Garra Tico47,L. Garrido36, C. Gaspar38, R. Gauld55, L. Gavardi9, E. Gersabeck11, M. Gersabeck54,T. Gershon48, Ph. Ghez4, A. Gianelle22, S. Gianı39, V. Gibson47, L. Giubega29, V.V. Gligorov38,C. Gobel60, D. Golubkov31, A. Golutvin53,31,38, A. Gomes1,a, H. Gordon38, C. Gotti20,M. Grabalosa Gandara5, R. Graciani Diaz36, L.A. Granado Cardoso38, E. Grauges36,G. Graziani17, A. Grecu29, E. Greening55, S. Gregson47, P. Griffith45, L. Grillo11, O. Grunberg62,B. Gui59, E. Gushchin33, Yu. Guz35,38, T. Gys38, C. Hadjivasiliou59, G. Haefeli39, C. Haen38,S.C. Haines47, S. Hall53, B. Hamilton58, T. Hampson46, X. Han11, S. Hansmann-Menzemer11,N. Harnew55, S.T. Harnew46, J. Harrison54, T. Hartmann62, J. He38, T. Head38, V. Heijne41,K. Hennessy52, P. Henrard5, L. Henry8, J.A. Hernando Morata37, E. van Herwijnen38, M. Heß62,

iii

A. Hicheur1, D. Hill55, M. Hoballah5, C. Hombach54, W. Hulsbergen41, P. Hunt55, N. Hussain55,D. Hutchcroft52, D. Hynds51, M. Idzik27, P. Ilten56, R. Jacobsson38, A. Jaeger11, J. Jalocha55,E. Jans41, P. Jaton39, A. Jawahery58, M. Jezabek26, F. Jing3, M. John55, D. Johnson55,C.R. Jones47, C. Joram38, B. Jost38, N. Jurik59, M. Kaballo9, S. Kandybei43, W. Kanso6,M. Karacson38, T.M. Karbach38, M. Kelsey59, I.R. Kenyon45, T. Ketel42, B. Khanji20,C. Khurewathanakul39, S. Klaver54, O. Kochebina7, M. Kolpin11, I. Komarov39,R.F. Koopman42, P. Koppenburg41,38, M. Korolev32, A. Kozlinskiy41, L. Kravchuk33,K. Kreplin11, M. Kreps48, G. Krocker11, P. Krokovny34, F. Kruse9, M. Kucharczyk20,26,38,k,V. Kudryavtsev34, K. Kurek28, T. Kvaratskheliya31, V.N. La Thi39, D. Lacarrere38,G. Lafferty54, A. Lai15, D. Lambert50, R.W. Lambert42, E. Lanciotti38, G. Lanfranchi18,C. Langenbruch38, B. Langhans38, T. Latham48, C. Lazzeroni45, R. Le Gac6, J. van Leerdam41,J.-P. Lees4, R. Lefevre5, A. Leflat32, J. Lefrancois7, S. Leo23, O. Leroy6, T. Lesiak26,B. Leverington11, Y. Li3, M. Liles52, R. Lindner38, C. Linn38, F. Lionetto40, B. Liu15, G. Liu38,S. Lohn38, I. Longstaff51, J.H. Lopes2, N. Lopez-March39, P. Lowdon40, H. Lu3, D. Lucchesi22,q,H. Luo50, A. Lupato22, E. Luppi16,f , O. Lupton55, F. Machefert7, I.V. Machikhiliyan31,F. Maciuc29, O. Maev30, S. Malde55, G. Manca15,e, G. Mancinelli6, M. Manzali16,f , J. Maratas5,J.F. Marchand4, U. Marconi14, C. Marin Benito36, P. Marino23,s, R. Marki39, J. Marks11,G. Martellotti25, A. Martens8, A. Martın Sanchez7, M. Martinelli41, D. Martinez Santos42,F. Martinez Vidal64, D. Martins Tostes2, A. Massafferri1, R. Matev38, Z. Mathe38,C. Matteuzzi20, A. Mazurov16,f , M. McCann53, J. McCarthy45, A. McNab54, R. McNulty12,B. McSkelly52, B. Meadows57,55, F. Meier9, M. Meissner11, M. Merk41, D.A. Milanes8,M.-N. Minard4, N. Moggi14, J. Molina Rodriguez60, S. Monteil5, D. Moran54, M. Morandin22,P. Morawski26, A. Morda6, M.J. Morello23,s, J. Moron27, R. Mountain59, F. Muheim50,K. Muller40, R. Muresan29, M. Mussini14, B. Muster39, P. Naik46, T. Nakada39,R. Nandakumar49, I. Nasteva2, M. Needham50, N. Neri21, S. Neubert38, N. Neufeld38,M. Neuner11, A.D. Nguyen39, T.D. Nguyen39, C. Nguyen-Mau39,p, M. Nicol7, V. Niess5,R. Niet9, N. Nikitin32, T. Nikodem11, A. Novoselov35, A. Oblakowska-Mucha27, V. Obraztsov35,S. Oggero41, S. Ogilvy51, O. Okhrimenko44, R. Oldeman15,e, G. Onderwater65, M. Orlandea29,J.M. Otalora Goicochea2, P. Owen53, A. Oyanguren64, B.K. Pal59, A. Palano13,c, F. Palombo21,t,M. Palutan18, J. Panman38, A. Papanestis49,38, M. Pappagallo51, C. Parkes54, C.J. Parkinson9,G. Passaleva17, G.D. Patel52, M. Patel53, C. Patrignani19,j , A. Pazos Alvarez37, A. Pearce54,A. Pellegrino41, M. Pepe Altarelli38, S. Perazzini14,d, E. Perez Trigo37, P. Perret5,M. Perrin-Terrin6, L. Pescatore45, E. Pesen66, K. Petridis53, A. Petrolini19,j ,E. Picatoste Olloqui36, B. Pietrzyk4, T. Pilar48, D. Pinci25, A. Pistone19, S. Playfer50,M. Plo Casasus37, F. Polci8, A. Poluektov48,34, E. Polycarpo2, A. Popov35, D. Popov10,B. Popovici29, C. Potterat2, A. Powell55, J. Prisciandaro39, A. Pritchard52, C. Prouve46,V. Pugatch44, A. Puig Navarro39, G. Punzi23,r, W. Qian4, B. Rachwal26, J.H. Rademacker46,B. Rakotomiaramanana39, M. Rama18, M.S. Rangel2, I. Raniuk43, N. Rauschmayr38,G. Raven42, S. Reichert54, M.M. Reid48, A.C. dos Reis1, S. Ricciardi49, A. Richards53, M. Rihl38,K. Rinnert52, V. Rives Molina36, D.A. Roa Romero5, P. Robbe7, A.B. Rodrigues1,E. Rodrigues54, P. Rodriguez Perez54, S. Roiser38, V. Romanovsky35, A. Romero Vidal37,M. Rotondo22, J. Rouvinet39, T. Ruf38, F. Ruffini23, H. Ruiz36, P. Ruiz Valls64, G. Sabatino25,l,J.J. Saborido Silva37, N. Sagidova30, P. Sail51, B. Saitta15,e, V. Salustino Guimaraes2,C. Sanchez Mayordomo64, B. Sanmartin Sedes37, R. Santacesaria25, C. Santamarina Rios37,E. Santovetti24,l, M. Sapunov6, A. Sarti18,m, C. Satriano25,n, A. Satta24, M. Savrie16,f ,D. Savrina31,32, M. Schiller42, H. Schindler38, M. Schlupp9, M. Schmelling10, B. Schmidt38,

iv

O. Schneider39, A. Schopper38, M.-H. Schune7, R. Schwemmer38, B. Sciascia18, A. Sciubba25,M. Seco37, A. Semennikov31, K. Senderowska27, I. Sepp53, N. Serra40, J. Serrano6, L. Sestini22,P. Seyfert11, M. Shapkin35, I. Shapoval16,43,f , Y. Shcheglov30, T. Shears52, L. Shekhtman34,V. Shevchenko63, A. Shires9, R. Silva Coutinho48, G. Simi22, M. Sirendi47, N. Skidmore46,T. Skwarnicki59, N.A. Smith52, E. Smith55,49, E. Smith53, J. Smith47, M. Smith54, H. Snoek41,M.D. Sokoloff57, F.J.P. Soler51, F. Soomro39, D. Souza46, B. Souza De Paula2, B. Spaan9,A. Sparkes50, F. Spinella23, P. Spradlin51, F. Stagni38, S. Stahl11, O. Steinkamp40,O. Stenyakin35, S. Stevenson55, S. Stoica29, S. Stone59, B. Storaci40, S. Stracka23,38,M. Straticiuc29, U. Straumann40, R. Stroili22, V.K. Subbiah38, L. Sun57, W. Sutcliffe53,K. Swientek27, S. Swientek9, V. Syropoulos42, M. Szczekowski28, P. Szczypka39,38, D. Szilard2,T. Szumlak27, S. T’Jampens4, M. Teklishyn7, G. Tellarini16,f , F. Teubert38, C. Thomas55,E. Thomas38, J. van Tilburg41, V. Tisserand4, M. Tobin39, S. Tolk42, L. Tomassetti16,f ,D. Tonelli38, S. Topp-Joergensen55, N. Torr55, E. Tournefier4, S. Tourneur39, M.T. Tran39,M. Tresch40, A. Tsaregorodtsev6, P. Tsopelas41, N. Tuning41, M. Ubeda Garcia38, A. Ukleja28,A. Ustyuzhanin63, U. Uwer11, V. Vagnoni14, G. Valenti14, A. Vallier7, R. Vazquez Gomez18,P. Vazquez Regueiro37, C. Vazquez Sierra37, S. Vecchi16, J.J. Velthuis46, M. Veltri17,h,G. Veneziano39, M. Vesterinen11, B. Viaud7, D. Vieira2, M. Vieites Diaz37,X. Vilasis-Cardona36,o, A. Vollhardt40, D. Volyanskyy10, D. Voong46, A. Vorobyev30,V. Vorobyev34, C. Voß62, H. Voss10, J.A. de Vries41, R. Waldi62, C. Wallace48, R. Wallace12,J. Walsh23, S. Wandernoth11, J. Wang59, D.R. Ward47, N.K. Watson45, D. Websdale53,M. Whitehead48, J. Wicht38, D. Wiedner11, G. Wilkinson55, M.P. Williams45, M. Williams56,F.F. Wilson49, J. Wimberley58, J. Wishahi9, W. Wislicki28, M. Witek26, G. Wormser7,S.A. Wotton47, S. Wright47, S. Wu3, K. Wyllie38, Y. Xie61, Z. Xing59, Z. Xu39, Z. Yang3,X. Yuan3, O. Yushchenko35, M. Zangoli14, M. Zavertyaev10,b, F. Zhang3, L. Zhang59,W.C. Zhang12, Y. Zhang3, A. Zhelezov11, A. Zhokhov31, L. Zhong3, A. Zvyagin38.

1Centro Brasileiro de Pesquisas Fısicas (CBPF), Rio de Janeiro, Brazil2Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil3Center for High Energy Physics, Tsinghua University, Beijing, China4LAPP, Universite de Savoie, CNRS/IN2P3, Annecy-Le-Vieux, France5Clermont Universite, Universite Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France6CPPM, Aix-Marseille Universite, CNRS/IN2P3, Marseille, France7LAL, Universite Paris-Sud, CNRS/IN2P3, Orsay, France8LPNHE, Universite Pierre et Marie Curie, Universite Paris Diderot, CNRS/IN2P3, Paris, France9Fakultat Physik, Technische Universitat Dortmund, Dortmund, Germany10Max-Planck-Institut fur Kernphysik (MPIK), Heidelberg, Germany11Physikalisches Institut, Ruprecht-Karls-Universitat Heidelberg, Heidelberg, Germany12School of Physics, University College Dublin, Dublin, Ireland13Sezione INFN di Bari, Bari, Italy14Sezione INFN di Bologna, Bologna, Italy15Sezione INFN di Cagliari, Cagliari, Italy16Sezione INFN di Ferrara, Ferrara, Italy17Sezione INFN di Firenze, Firenze, Italy18Laboratori Nazionali dell’INFN di Frascati, Frascati, Italy19Sezione INFN di Genova, Genova, Italy20Sezione INFN di Milano Bicocca, Milano, Italy21Sezione INFN di Milano, Milano, Italy22Sezione INFN di Padova, Padova, Italy23Sezione INFN di Pisa, Pisa, Italy

v

24Sezione INFN di Roma Tor Vergata, Roma, Italy25Sezione INFN di Roma La Sapienza, Roma, Italy26Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krakow, Poland27AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science,Krakow, Poland28National Center for Nuclear Research (NCBJ), Warsaw, Poland29Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele, Romania30Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia31Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia32Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia33Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN), Moscow, Russia34Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State University, Novosibirsk, Russia35Institute for High Energy Physics (IHEP), Protvino, Russia36Universitat de Barcelona, Barcelona, Spain37Universidad de Santiago de Compostela, Santiago de Compostela, Spain38European Organization for Nuclear Research (CERN), Geneva, Switzerland39Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne, Switzerland40Physik-Institut, Universitat Zurich, Zurich, Switzerland41Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands42Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, TheNetherlands43NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine44Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine45University of Birmingham, Birmingham, United Kingdom46H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom47Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom48Department of Physics, University of Warwick, Coventry, United Kingdom49STFC Rutherford Appleton Laboratory, Didcot, United Kingdom50School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom51School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom52Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom53Imperial College London, London, United Kingdom54School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom55Department of Physics, University of Oxford, Oxford, United Kingdom56Massachusetts Institute of Technology, Cambridge, MA, United States57University of Cincinnati, Cincinnati, OH, United States58University of Maryland, College Park, MD, United States59Syracuse University, Syracuse, NY, United States60Pontifıcia Universidade Catolica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil, associated to 2

61Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China, associated to 3

62Institut fur Physik, Universitat Rostock, Rostock, Germany, associated to 11

63National Research Centre Kurchatov Institute, Moscow, Russia, associated to 31

64Instituto de Fisica Corpuscular (IFIC), Universitat de Valencia-CSIC, Valencia, Spain, associated to 36

65KVI - University of Groningen, Groningen, The Netherlands, associated to 41

66Celal Bayar University, Manisa, Turkey, associated to 38

aUniversidade Federal do Triangulo Mineiro (UFTM), Uberaba-MG, BrazilbP.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, RussiacUniversita di Bari, Bari, ItalydUniversita di Bologna, Bologna, ItalyeUniversita di Cagliari, Cagliari, ItalyfUniversita di Ferrara, Ferrara, Italy

vi

gUniversita di Firenze, Firenze, ItalyhUniversita di Urbino, Urbino, ItalyiUniversita di Modena e Reggio Emilia, Modena, ItalyjUniversita di Genova, Genova, ItalykUniversita di Milano Bicocca, Milano, ItalylUniversita di Roma Tor Vergata, Roma, ItalymUniversita di Roma La Sapienza, Roma, ItalynUniversita della Basilicata, Potenza, ItalyoLIFAELS, La Salle, Universitat Ramon Llull, Barcelona, SpainpHanoi University of Science, Hanoi, Viet NamqUniversita di Padova, Padova, ItalyrUniversita di Pisa, Pisa, ItalysScuola Normale Superiore, Pisa, ItalytUniversita degli Studi di Milano, Milano, Italy

vii

1 Introduction

Heavy baryons are systems of three quarks, among which at least one is c or b. The quarksare bound by the strong interaction, which is described by quantum chromodynamics(QCD). Hadron lifetimes are among the most useful inputs to tune the parameters ofQCD models. A powerful approach for theoretical predictions of b-hadron lifetime ratiosis the heavy quark expansion (HQE) framework [1] which allows calculations in powers ofΛQCD/mb, where ΛQCD is the energy scale at which QCD becomes non-perturbative andmb is the b-quark mass. With the exception of the b hadrons containing a c quark, thepredictions for the various b-hadron lifetimes only start to differ at the order Λ2

QCD/m2b

and are equal within several percent.So far only the most abundantly produced b baryon, the Λ0

b with quark content udb, hasbeen studied in detail. Early Λ0

b lifetime measurements [2–5] yielded values significantlysmaller than the B-meson lifetime determinations, casting doubt on the HQE and causingincreased theoretical activity [6–11]. More recent determinations of the ratio between theΛ0b and B0 lifetimes, for instance that of Ref. [12], are in much better agreement with the

original predictions. However, less information exists on the strange b baryons, which areless abundantly produced than Λ0

b baryons. In particular for the Ξ−b (dsb) and Ω−b (ssb)baryons only a few theoretical lifetime calculations are available [7, 8, 13]. Furthermore,most of the predictions date back to the 1990s and have limited precision, with centralvalues ranging from 1.0 ps to 1.7 ps. New experimental data are needed to provide morestringent constraints on the models.

The weakly decaying Ξ−b and Ω−b baryons were observed for the first time at theTevatron experiments CDF [14, 15] and D0 [16, 17]. Prior to these first observations,the average Ξb lifetime (including Ξ−b and Ξ0

b ) was measured by the LEP experimentsDELPHI [18, 19] and ALEPH [20] using partially reconstructed decays. So far the onlyexclusive lifetime measurement of the strange b baryons Ξ−b and Ω−b has been made bythe CDF experiment [15, 21]. Recently, LHCb demonstrated its ability to reconstructa significant number of Ξ−b and Ω−b baryons [22] and to measure precisely b-hadronlifetimes [23].

In this Letter we present lifetime measurements of the Ξ−b and Ω−b baryons reconstructedin the Ξ−b → J/ψΞ− and Ω−b → J/ψΩ− decay modes. The daughter particles arereconstructed in the decay modes J/ψ → µ+µ−, Ξ− → Λπ−, Ω− → ΛK− and Λ→ pπ−.Unless specified otherwise, charge-conjugated states are implied throughout.

2 Detector and event samples

The LHCb detector [24] is a single-arm forward spectrometer covering the pseudorapidityrange 2 < η < 5, designed for the study of particles containing b or c quarks. The detectorincludes a high-precision tracking system consisting of a silicon-strip vertex detector sur-rounding the pp interaction region, a large-area silicon-strip detector located upstream ofa dipole magnet with a bending power of about 4 Tm, and three stations of silicon-stripdetectors and straw drift tubes [25] placed downstream of the magnet. The combined

1

tracking system provides a momentum measurement with a relative uncertainty thatvaries from 0.4% at low momentum, p, to 0.6% at 100 GeV/c, and an impact parametermeasurement with a resolution of 20µm for charged particles with large transverse mo-mentum, pT. Different types of charged hadrons are distinguished using information fromtwo ring-imaging Cherenkov detectors [26]. Photon, electron and hadron candidates areidentified by a calorimeter system consisting of scintillating-pad and preshower detectors,an electromagnetic calorimeter and a hadronic calorimeter. Muons are identified by asystem composed of alternating layers of iron and multiwire proportional chambers [27].

The trigger consists of a hardware stage, based on information from the calorimeterand muon systems, followed by a software stage, which applies a full event reconstruction.For this measurement, events are first required to pass the hardware trigger, which selectsmuons with high transverse momentum. In the subsequent software stage, events areretained by two independent sets of requirements. One demands a muon candidate withmomentum larger than 6 GeV/c that, combined with another oppositely charged muoncandidate, yields a dimuon mass larger than 2.7 GeV/c2. The other requires a muoncandidate with momentum larger than 8 GeV/c and an impact parameter above 100µmwith respect to all of the primary pp interaction vertices (PVs) in the event. Finally, forall candidates, two muons are required to form a vertex that is significantly displaced fromthe PVs.

The Ξ−b and Ω−b lifetime measurements presented here are based on the combinationof the two data sets recorded in 2011 and 2012. During the year 2011 the LHCb detectorrecorded pp collisions at a centre-of-mass energy of

√s = 7 TeV corresponding to an

integrated luminosity of 1 fb−1. In 2012, it recorded approximately twice as much data at√s = 8 TeV. Between 2011 and 2012, an improvement in the tracking algorithm of the

vertex detector was introduced, leading to different trigger and reconstruction efficienciesin the two data sets. The polarity of the dipole magnet was periodically inverted so thatroughly half of the data was collected with each polarity.

Four million Ξ−b (Ω−b ) signal events, corresponding to approximately 135 fb−1

(1700 fb−1) of LHCb data, were simulated with each of the 2011 and 2012 data tak-ing conditions. The pp collisions are generated using Pythia [28] with a specific LHCbconfiguration [29]. Decays of hadronic particles are described by EvtGen [30], in whichfinal state radiation is generated using Photos [31]. The interaction of the generatedparticles with the detector and its response are implemented using the Geant4 toolkit [32]as described in Ref. [33].

3 Reconstruction and selection

The J/ψ → µ+µ− decay is reconstructed from oppositely charged particles that leavedeposits in the vertex detector, the tracking stations and the muon system. The hyperonsin the b-baryon decay chains (Ξ−, Ω− and Λ) are long-lived; approximately 10% of allreconstructed b-baryon candidates are reconstructed with all tracks leaving deposits inthe vertex detector. To retain as many candidates as possible, tracks that have no vertex

2

detector information are also considered for the reconstruction of the hyperon decays.The Ξ−b and Ω−b candidates are selected through identical requirements except for the

ranges in which the baryon masses are reconstructed. In addition, for the Ω−b case thecharged track from the Ω− decay is required to be identified as a kaon by the particleidentification detectors, removing more than 95% of the background pions.

All final-state tracks are required to satisfy minimal quality criteria and kinematicrequirements. In order to reduce backgrounds from combinations of random tracks, thedecay vertices are required to be well reconstructed. The J/ψ , Ξ−, Ω− and Λ candidatesare selected within mass windows of ±60 MeV/c2, ±11 MeV/c2, ±11 MeV/c2 and ±6 MeV/c2,respectively, around the corresponding known masses [34].

The hadronic final-state tracks are required to have large impact parameters withrespect to the PV associated with the b-baryon candidate. The associated PV is chosen asthe PV giving the smallest increase in the χ2 of the PV fit when the b baryon is included.The associated PV is also required to be isolated with respect to other PVs and consistentwith the nominal interaction region.

The b-baryon mass is computed after a complete kinematic fit of the decay chain [35]in which the masses of both daughter particles are constrained to their known values [34].No constraint is applied on the Λ mass. The resulting b-baryon invariant mass is requiredto lie in the range 5600–6000 MeV/c2 for Ξ−b candidates and 5800–6300 MeV/c2 for Ω−bcandidates. The decay time of the b-baryon candidate, t, is computed from the decaylength, d, as

t =d

βγc=m

pd , (1)

where m is the reconstructed mass and p the reconstructed momentum of the b-baryoncandidate. The decay length itself is obtained from a refit of the decay chain with nomass constraints in order to keep the correlation between the reconstructed decay timeand mass at a negligible level. Backgrounds are further suppressed by requiring this decaychain fit to be of good quality. The reconstructed decay time is required to lie in the range0.3–14 ps. The lower bound of this decay-time range helps to suppress background comingfrom random combinations of tracks with real J/ψ mesons produced at the PV. In lessthan 1% of the cases, more than one candidate per event pass the selection criteria andonly the candidate with the best decay chain fit result is retained.

4 Resolution and efficiency

The decay time resolution is obtained by fitting the difference between the reconstructeddecay time, t, and the true decay time, ttrue, in simulated events. The fit model is a singleGaussian function G(t− ttrue, t, σres) where the mean, t, and the width, σres, are left free.For both considered decay modes and both data-taking periods, t is compatible with zeroand σres is close to 50 fs.

A bias in the measured lifetime can arise from a non-uniform efficiency as a functionof the b-baryon decay time [23]. There are two types of inefficiencies which alter the

3

decay time distribution. The first affects mostly candidates with small decay times and isinduced by the requirements of the trigger that reject predominantly short-lived b baryons.The second affects mostly candidates with large decay times and is due to the geometricaldetector acceptance, the reconstruction process and the selection criteria that lead to alower efficiency for long-lived b baryons. Both effects are estimated and corrected for usingsimulation. This approach is validated with several techniques described in Sec. 6.

The two trigger selections used for these lifetime measurements include a requirementon the decay length significance of the J/ψ meson. In addition, one selection also containsa requirement on the impact parameter of the muons from the J/ψ decay. The tworequirements induce an inefficiency at low values of the reconstructed decay time. To assessthis effect, simulated events undergo an emulation of the trigger. In addition, an unbiasedtrigger selection is used to remove the contribution from the detector acceptance, thereconstruction and the selection. The resulting efficiency as a function of the reconstructeddecay time is fitted with an empirical function of the form

ε1(t) = erf( a · (t− t0)n ) , where erf(u) =2√π

∫ u

0

e−x2

dx , (2)

and where a, t0 and n are free parameters. The distributions of the decay products of theb baryons depend on the decay mode and on the year of data taking. This dependenceslightly affects the shape of the efficiency as a function of the reconstructed decay time.Thus separate efficiency functions are obtained for the two decay modes, for the two datataking periods and for the two trigger selections. The efficiency functions correspondingto the 2012 data taking conditions for the Ξ−b case are shown in Fig. 1 as an example.

The dependence of the efficiency on the decay time due to the geometrical detectoracceptance, the reconstruction and the selection is found to be well described with a linearfunction,

ε2(t) = 1 + βt . (3)

The free parameter β is obtained by fitting a function proportional to ε2(t) ·∫∞0

exp(−ttrue/τgen)G(t− ttrue, 0, σres) dttrue to the reconstructed decay time distributionof simulated signal events that are generated with a mean lifetime of τgen and that arefully reconstructed and selected. Separate values for β are determined for the two differentdecay modes and the two data-taking periods and are given in Table 1. The efficiencyfunctions corresponding to the 2012 data taking conditions for the Ξ−b and Ω−b cases areshown in Fig. 2 as an example.

4

decay time [ps]−

bΞ0.5 1 1.5 2

Arb

itra

ry u

nit

0

0.2

0.4

0.6

0.8

1

LHCb simulation−

Ξ ψ J/→ −

bΞ2012 conditions

decay time [ps]−

bΞ1 2 3 4

Arb

itra

ry u

nit

0

0.1

0.2

0.3

0.4

0.5 LHCb simulation−

Ξ ψ J/→ −

bΞ2012 conditions

Figure 1: Efficiency for triggering simulated Ξ−b events as a function of the reconstructed decaytime under the 2012 data-taking conditions. Only a restricted decay-time range is shown in orderto emphasize the region where the effect is large. The left panel shows the efficiency for eventspassing the trigger with only the requirement on the J/ψ vertex displacement. The right panelshows the efficiency for events passing the trigger with requirements on both the J/ψ vertexdisplacement and the muon impact parameter and required to not pass the other trigger. Theresults of fits with functions proportional to that given in Eq. 2 are overlaid.

decay time [ps]−

bΞ5 10

Arb

itra

ry u

nit

0

0.05

0.1

0.15

0.2

0.25

0.3

LHCb simulation−

Ξ ψ J/→ −

bΞ

2012 conditions

decay time [ps]−

bΩ5 10

Arb

itra

ry u

nit

0

0.05

0.1

0.15

0.2

0.25

0.3

LHCb simulation−

Ω ψ J/→ −

bΩ

2012 conditions

Figure 2: Efficiency due to the detector acceptance, reconstruction and selection of simulatedΞ−b (left) and Ω−b (right) events as a function of the reconstructed decay time under the 2012data-taking conditions. The results of fits with functions proportional to that given in Eq. 3 areoverlaid.

5

Table 1: Fitted β values (in ps−1) for the efficiency described in Eq. 3 extracted from simulatedΞ−b and Ω−b decays. The quoted uncertainties are statistical only.

Decay mode 2011 conditions 2012 conditionsΞ−b → J/ψΞ− (−13.1± 4.8)× 10−3 (−20.2± 5.0)× 10−3

Ω−b → J/ψΩ− (−23.3± 3.5)× 10−3 (−19.3± 3.9)× 10−3

5 Lifetime fit

The lifetime is extracted from a two-dimensional extended maximum likelihood fit tothe unbinned b-baryon mass and decay-time distributions. The mass and decay timeare computed with the techniques described in Sec. 3. Assuming a negligible correlationbetween these two quantities, the two-dimensional probability density functions for thesignal and the background are each written as the product of a mass term and a decay-timeterm.

For the mass distribution, the signal is described with a single Gaussian function inwhich the mean and width are free parameters. Independent means are used for the datarecorded in 2011 and in 2012, since different calibrations are applied. The background inthe mass distribution is modelled with an exponential function. The signal in the decaytime distribution is described with the product of the efficiency functions (described inEqs. 2 and 3) and a convolution between an exponential function and a Gaussian functiondescribing the decay time resolution,

S(t) = N · ε1(t) · ε2(t) ·∫ ∞0

e−ttrue/τG(t− ttrue, 0, σres) dttrue , (4)

where N is a normalisation parameter and τ the fitted lifetime. The decay time resolutionσres is fixed to the value obtained in simulation, separately for each decay mode and eachyear of data taking. The background in the decay time distribution is modelled withthe sum of two exponential functions that are also convolved with the fixed decay timeresolution function. With the exception of σres, all background parameters are left freein the fit. A study based on pseudo-experiments shows that no observable bias to themeasured lifetimes arises from the fit model itself.

The fit is performed for all selected b-baryon candidates. Due to the low signal yields,asymmetric uncertainties are calculated. Figure 3 shows the invariant mass and decaytime distributions and the projection of the fit results for the Ξ−b and Ω−b baryons. Table 2displays the fit result for the relevant signal parameters.

As a consistency check for the fitting method, a measurement of the Λ0b → J/ψΛ

lifetime is performed using the same data set and techniques as presented in this paper.The measured Λ0

b lifetime is consistent with the world average [34] and with recentmeasurements from LHCb [12,23].

6

]2c) [MeV/

−Ξ ψM(J/

5600 5700 5800 5900 6000

)2c

Can

did

ate

s /

( 8

MeV

/

0

20

40

60

80

100

120

140

LHCb−

Ξ ψ J/→ −

bΞ

]2c) [MeV/

−Ω ψM(J/

5800 5900 6000 6100 6200 6300

)2c

Can

did

ate

s /

( 1

0 M

eV

/

0

5

10

15

20

25

30

35LHCb

−Ω ψ J/→

−

bΩ

decay time [ps]−

bΞ5 10

Can

did

ates

/ (

0.2

7 p

s )

1

10

210LHCb

−Ξ ψ J/→

−

bΞSignal region

Data

Signal

BackgroundTotal

decay time [ps]−

bΩ5 10

Can

did

ates

/ (

0.2

7 p

s )

1

10

LHCb−

Ω ψ J/→ −

bΩSignal region

Data

Signal

BackgroundTotal

decay time [ps]−

bΞ5 10

Can

did

ates

/ (

0.2

7 p

s )

1

10

210

310

LHCb−

Ξ ψ J/→ −

bΞBackground region

Data

Signal

BackgroundTotal

decay time [ps]−

bΩ5 10

Can

did

ates

/ (

0.2

7 p

s )

1

10

210LHCb

−Ω ψ J/→

−

bΩBackground region

Data

Signal

BackgroundTotal

Figure 3: Distributions of the reconstructed invariant mass (top) and decay time (middle andbottom) of the Ξ−b → J/ψΞ− (left) and Ω−b → J/ψΩ− (right) candidates. The middle (bottom)panels show the decay time distributions of the candidates in the signal (background) massregions. The signal mass region is defined as 5773–5825 MeV/c2 for Ξ−b and 6028–6073 MeV/c2

for Ω−b candidates, as shown by the vertical dotted lines in the mass distributions, whereas thebackground mass regions include all other candidates. The results of the fits are overlaid.

7

Table 2: Fitted parameters with statistical uncertainties for the Ξ−b and Ω−b signals.

Parameter Ξ−b → J/ψΞ− Ω−b → J/ψΩ−

Signal yield 313± 20 58± 8Mass resolution 8.5± 0.5 MeV/c2 7.5± 1.0 MeV/c2

Lifetime (τ) 1.55 +−

0.100.09 ps 1.54 +

−0.260.21 ps

6 Systematic uncertainties

Unless specified otherwise, the evaluation of the systematic uncertainties is performedby varying in turn each fixed parameter of the fit within its uncertainty and taking thechange in the fit result. The total systematic uncertainty is obtained as the quadratic sumof the individual contributions. Distributions of results from fits to pseudo-experimentsare used for the leading contributions (efficiencies and modelling) in order to ensure thatthey are not incorrectly estimated due to a statistical fluctuation of the data. A summaryof all contributions to the total systematic uncertainty is given in Table 3.

Two contributions are considered as uncertainties due to the trigger efficiency. Onearises from the finite size of the simulation samples and is taken into account by varyingthe parameters of the efficiency function ε1 within their uncertainties. The other is due toa potential discrepancy between data and simulation. This second contribution is assessedby repeating the fit using an efficiency obtained from a data sample of B0 → J/ψK0

S

decays that are topologically similar to the b-baryon decays of interest and reconstructedin data collected by the same trigger. In this case, extracting the efficiency from data ispossible because a large sample, selected with triggers that do not bias the decay timedistribution, is available (see Ref. [23]).

Two contributions are considered as uncertainties in determining the reconstruction

Table 3: Systematic uncertainties on the lifetime measurements in fs. For the total uncertainty,all the contributions are summed in quadrature.

Source Ξ−b → J/ψΞ− Ω−b → J/ψΩ−

Trigger efficiency 9.9 6.5Reconstruction and selection efficiency 29.0 45.0Signal modelling 5.9 11.4Combinatorial background modelling 3.0 3.0Cross-feed background 0.1 11.1Detector length scale 0.3 0.3Total 31.4 48.3

8

and selection efficiency. One arises from the finite size of the simulation samples and isassessed by varying the parameter β within its statistical uncertainty. The other takesinto account the quality of the simulation of the geometrical detector acceptance, thereconstruction process and the selection. For this second contribution, the β parameter isvaried by ±50% to cover any possible discrepancy between data and simulation [36]. Thetotal systematic uncertainty related to the reconstruction and selection efficiency, taken asthe quadratic sum of the two contributions, is larger for Ω−b than for Ξ−b decays due tothe larger value of the β parameter for Ω−b in 2011 data.

Several alternative fits are performed to assess the systematic uncertainties relatedto the signal modelling. In one fit, the Gaussian function describing the signal modelin the b-baryon mass distribution is replaced by the sum of two Gaussian functions ofcommon mean. The widths and the relative yields are left free. To assess the effect ofthe decay time resolution function, the widths of the corresponding Gaussian functionsare varied by ±10%. In another alternative fit, this resolution function is taken as thesum of two Gaussian functions instead of one, where the parameters are still taken fromsimulation. This takes into account potential tails in the decay time resolution distribution.All variations of the function describing the decay time resolution change the fit result bya negligible amount. Therefore the systematic uncertainty related to the signal modellingis dominated by the signal description in the mass distribution.

The systematic uncertainties due to combinatorial background are taken into accountwith three alternative fit models. In the first, the background in the mass distributionis described with a linear function. In another fit the background is modelled with twodifferent exponential functions for the two different years of data taking. As an alternativedescription of the background in the decay time distribution, three exponential functions,instead of two, are convolved with the Gaussian resolution.

The only other significant background expected is a cross-feed between the two b-baryondecays. The rate and mass distribution of the cross-feed backgrounds is determined byreconstructing simulated decays of one channel under the hypothesis of the other. Accordingto simulation, 0.24 (3.0) Ω−b (Ξ−b ) decays are expected to be reconstructed as Ξ−b (Ω−b )over the full mass range. The effect of this background on the lifetime measurement isdetermined by injecting simulated background events into a fit of simulated signal eventsand taking the observed bias as the systematic uncertainty.

The overall length scale of the vertex detector is known with a relative precision of0.02% [23]. As the measured decay length is directly proportional to the overall length scale,this precision directly translates into a relative uncertainty on the lifetime measurements.

9

7 Conclusion

Using data samples recorded during the years 2011 and 2012, corresponding to an integratedluminosity of 3 fb−1, the lifetimes of the weakly decaying Ξ−b and Ω−b baryons are measuredto be

τ(Ξ−b ) = 1.55 +0.10−0.09 (stat)± 0.03 (syst) ps,

τ(Ω−b ) = 1.54 +0.26−0.21 (stat)± 0.05 (syst) ps.

These are the most precise lifetime measurements of these b baryons to date. Bothmeasurements are in agreement with the previous experimental results, in particularwith the most recent ones from the CDF collaboration of τ(Ξ−b ) = 1.32 ± 0.14 ps andτ(Ω−b ) = 1.66±0.47 ps [21]. The measurements also lie in the range predicted by theoreticalcalculations [7, 8, 13].

Acknowledgements

We express our gratitude to our colleagues in the CERN accelerator departments forthe excellent performance of the LHC. We thank the technical and administrative staffat the LHCb institutes. We acknowledge support from CERN and from the nationalagencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); NSFC (China); CNRS/IN2P3and Region Auvergne (France); BMBF, DFG, HGF and MPG (Germany); SFI (Ireland);INFN (Italy); FOM and NWO (The Netherlands); SCSR (Poland); MEN/IFA (Romania);MinES, Rosatom, RFBR and NRC “Kurchatov Institute” (Russia); MinECo, XuntaGaland GENCAT (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC and theRoyal Society (United Kingdom); NSF (USA). We also acknowledge the support receivedfrom EPLANET, Marie Curie Actions and the ERC under FP7. The Tier1 computingcentres are supported by IN2P3 (France), KIT and BMBF (Germany), INFN (Italy),NWO and SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom). We areindebted to the communities behind the multiple open source software packages on whichwe depend. We are also thankful for the computing resources and the access to softwareR&D tools provided by Yandex LLC (Russia).

10

References

[1] M. Neubert, B decays and the Heavy-Quark Expansion, Adv. Ser. Direct. High EnergyPhys. 15 (1998) 239, arXiv:hep-ph/9702375.

[2] ALEPH collaboration, D. Buskulic et al., Measurements of the b baryon lifetime, Phys.Lett. B357 (1995) 685.

[3] OPAL collaboration, R. Akers et al., A measurement of the Λ0b lifetime, Phys. Lett.

B353 (1995) 402.

[4] DELPHI collaboration, P. Abreu et al., Determination of the average lifetime of bbaryons, Z. Phys. C71 (1996) 199.

[5] CDF collaboration, F. Abe et al., Measurement of Λ0b lifetime using Λ0

b → Λ+c l−ν,

Phys. Rev. Lett. 77 (1996) 1439.

[6] G. Altarelli et al., Failure of local duality in inclusive non-leptonic heavy flavour, Phys.Lett. B382 (1996) 409, arXiv:hep-ph/9604202.

[7] H.-Y. Cheng, A phenomenological analysis of heavy hadron lifetimes, Phys. Rev. D56(1997) 2783, arXiv:hep-ph/9704260.

[8] T. Ito, M. Matsuda, and Y. Matsui, New possibility of solving the problem of lifetimeratio τ(Λ0

b)/τ(Bd), Prog. Theor. Phys. 99 (1998) 271, arXiv:hep-ph/9705402.

[9] N. Uraltsev, Topics in the Heavy Quark Expansion, arXiv:hep-ph/0010328.

[10] F. Gabbiani, A. I. Onishchenko, and A. A. Petrov, Λ0b lifetime puzzle in heavy-quark

expansion, Phys. Rev. D68 (2003) 114006, arXiv:hep-ph/0303235.

[11] F. Gabbiani, A. I. Onishchenko, and A. A. Petrov, Spectator effects and lifetimes ofheavy hadrons, Phys. Rev. D70 (2004) 094031, arXiv:hep-ph/0407004.

[12] LHCb collaboration, R. Aaij et al., Precision measurement of the ratio of the Λ0b to

B0 lifetimes, Phys. Lett. B734 (2014) 122, arXiv:1402.6242.

[13] I. I. Bigi, The QCD perspective on lifetimes of heavy-flavour hadrons,arXiv:hep-ph/9508408.

[14] CDF collaboration, T. Aaltonen et al., Observation and mass measurement of thebaryon Ξ−b , Phys. Rev. Lett. 99 (2007) 052002, arXiv:0707.0589.

[15] CDF collaboration, T. Aaltonen et al., Observation of the Ω−b baryon and measure-ment of the properties of the Ξ−b and Ω−b baryons, Phys. Rev. D80 (2009) 072003,arXiv:0905.3123.

11

[16] D0 collaboration, V. Abazov et al., Direct observation of the strange b baryon Ξ−b ,Phys. Rev. Lett. 99 (2007) 052001, arXiv:0706.1690.

[17] D0 collaboration, V. Abazov et al., Observation of the doubly strange b baryon Ω−b ,Phys. Rev. Lett. 101 (2008) 232002, arXiv:0808.4142.

[18] DELPHI collaboration, P. Abreu et al., Production of strange B baryons decayinginto Ξ∓ - l∓ pairs at LEP, Z. Phys. C68 (1995) 541.

[19] DELPHI collaboration, J. Abdallah et al., Production of Ξ0c and Ξb in Z decays and

lifetime measurement of Ξb, Eur. Phys. J. C44 (2005) 299, arXiv:hep-ex/0510023.

[20] ALEPH collaboration, D. Buskulic et al., Strange b baryon production and lifetime inZ decays, Phys. Lett. B384 (1996) 449.

[21] CDF collaboration, T. Aaltonen et al., Mass and lifetime measurements of bottomand charm baryons in pp collisions at

√s = 1.96 TeV, Phys. Rev. D89 (2014) 072014,

arXiv:1403.8126.

[22] LHCb collaboration, R. Aaij et al., Measurements of the Λ0b , Ξ−b and Ω−b baryon

masses, Phys. Rev. Lett. 110 (2013) 182001, arXiv:1302.1072.

[23] LHCb collaboration, R. Aaij et al., Measurements of the B+, B0, B0s meson and Λ0

b

baryon lifetimes, JHEP 04 (2014) 114, arXiv:1402.2554.

[24] LHCb collaboration, A. A. Alves Jr. et al., The LHCb detector at the LHC, JINST 3(2008) S08005.

[25] R. Arink et al., Performance of the LHCb Outer Tracker, JINST 9 (2014) P01002,arXiv:1311.3893.

[26] M. Adinolfi et al., Performance of the LHCb RICH detector at the LHC, Eur. Phys.J. C73 (2013) 2431, arXiv:1211.6759.

[27] A. A. Alves Jr. et al., Performance of the LHCb muon system, JINST 8 (2013) P02022,arXiv:1211.1346.

[28] T. Sjostrand, S. Mrenna, and P. Skands, PYTHIA 6.4 physics and manual, JHEP05 (2006) 026, arXiv:hep-ph/0603175; T. Sjostrand, S. Mrenna, and P. Skands,A brief introduction to PYTHIA 8.1, Comput. Phys. Commun. 178 (2008) 852,arXiv:0710.3820.

[29] I. Belyaev et al., Handling of the generation of primary events in Gauss, the LHCbsimulation framework, Nuclear Science Symposium Conference Record (NSS/MIC)IEEE (2010) 1155.

[30] D. J. Lange, The EvtGen particle decay simulation package, Nucl. Instrum. Meth.A462 (2001) 152.

12

[31] P. Golonka and Z. Was, PHOTOS Monte Carlo: a precision tool for QED correctionsin Z and W decays, Eur. Phys. J. C45 (2006) 97, arXiv:hep-ph/0506026.

[32] Geant4 collaboration, J. Allison et al., Geant4 developments and applications, IEEETrans. Nucl. Sci. 53 (2006) 270; Geant4 collaboration, S. Agostinelli et al., Geant4: asimulation toolkit, Nucl. Instrum. Meth. A506 (2003) 250.

[33] M. Clemencic et al., The LHCb simulation application, Gauss: design, evolution andexperience, J. Phys. Conf. Ser. 331 (2011) 032023.

[34] Particle Data Group, J. Beringer et al., Review of particle physics, Phys. Rev. D86(2012) 010001, and 2013 partial update for the 2014 edition.

[35] W. D. Hulsbergen, Decay chain fitting with a Kalman filter, Nucl. Instrum. Meth.A552 (2005) 566, arXiv:physics/0503191.

[36] LHCb collaboration, R. Aaij et al., Measurement of the CP -violating phase φs in thedecay B0

s → J/ψφ, Phys. Rev. Lett. 108 (2012) 101803, arXiv:1112.3183.

13